This invention relates to microwave solid-state masers, and more particularly to improved bandwidth and gain control of a traveling-wave maser amplifier.
The instantaneous bandwidth of a maser is determined by the maser material linewidth, the shape (or uniformity) of the magnetic field required for maser operation, and the electronic gain at which the maser operates. A thorough discussion of methods for increasing the bandwidth of a maser can be found in Microwave Solid State Masers by S. E. Siegman, McGraw-Hill Book Co., Inc., pp. 326-331, 395. Siegman shows that operation of a maser using ruby (linewidth .perspectiveto. 50 MHz) in a uniform magnetic field at high gain (more than 40 dB) results in a 3-dB bandwidth of less than 20 MHz. Attempts to increase bandwidth always result in substantial gain reductions.
Considerable effort has been devoted to the task of optimizing the gain versus bandwidth trade-off. Bandwidth and gain value adjustment of previous masers has been achieved by a combination of iron shims and field staggering coils to alter the shape of the magnetic field required for the maser operation.
The previous methods are time consuming and require different shims or field staggering coil placement for each maser structure. Nevertheless, stagger tuning remains the most efficient way to adjust the gain and bandwidth of a maser. What is required is a method for effectively achieving stagger tuning without the need for altering the placement of shims or field staggering coils. Ideally, the method employed should permit tuning after assembly of the maser has been completed, and even after the maser has been installed in the system in which it is operate. It should also permit tuning a maser of some basic design for operation in different systems without altering its design.